Method of making prefabricated building unit

ABSTRACT

A PROCESS FOR MAKING PREFABRICATED UNITS FOR USE IN ERECTING PREFABRICATED BUILDINGS COMPRISES FORMING A STRUCTURAL STEEL FRAME, PREFERABLY MADE FROM TUBULAR STEEL RECTANGULAR FRAME SECTIONS, AND PLACING THE FRAME HORIZONTALLY IN AN OPEN TOPED MOULD HAVING A FLAT BOTTOM AND VERTICAL SIDES WHICH ARE ARRANGED SO THAT THE FRAME CAN BE PLACED WITH ITS OUTER EDGES PROJECTING BEYOND THE PLANES OF THE SIDES OF THE MOULD AND SO THAT THE LOWER FACE OF THE FRAME IS CLEAR OF AND PARALLEL TO THE FLAT BOTTOM OF THE MOULD. A LIGHT WEIGHT CONCRETE MIX IS THEN POURED INTO THE MOULD SO THAT THE MIX FILLS THE SPACE BETWEEN THE BOTTOM OF THE MOULD AND THE LOWER FACE OF THE FRAME AND ALOS FILLS AT LEAST PART OF THE SPACE BOUNDD BY THE FRAME SO THAT THE STEEL MEMBERS FORMING THE FRAME ARE AT LEAST PARTLY EMBEDDED IN THE MIX. THE MIX IS THEN ALLOWED TO SET AND THE UNIT IS REMOVED FROM THE MOULD. THE MIX IS OF SUCH A CONSTITUENCY TAT, ON SETTING, A SMOOTH SURFACE IS FORMED IN CONTACT WITH THE BOTTOM OF THE MOULD. A UNIT IS THUS FORMED WITH THE OUTER EDGES OF THE FRAME PROJECTING BEYOUND THE CONCRETE IN-FILLING TO FACILITATE THE WELDING TOGETHER OF ADJACENT UNITS AR RITGHT ANGLES TO EACH OTHER, AND WITH AN INNER FACE WHICH IS SUFFICIENTLY SMOOTH TO SERVE AS A CEILING OR WALL OF A ROOM WITHOUT NEED OF A FURTHER FINISH SUCH AS A PLASTER COATING TO BE APPLIED TO THE SURFACE.

Oct. 12, I971 T.V.THOMASON 3,611,533

METHOD OF MAKING PREFABRICATED BUiLDING UNIT Filed April 5, 1969 I 2 Sheets-Sheet 1 Oct. 12, 1971 T, v, THOMASQN 3,611,533

METHOD OF MAKING PREFABRICATED BUILDING UNIT -2 Sheets-Sheet 2 Filed April 5, 1969 MMMW% M %M%H% MQZ K. v m m Q \QQQ MJIQQ United States Patent US. Cl. 29-455 16 Claims ABSTRACT OF THE DISCLOSURE A process for making prefabricated units for use in erecting prefabricated buildings comprises forming a structural steel frame, preferably made from tubular steel rectangular frame sections, and placing the frame horizontally in an open topped mould having a flat bottom and vertical sides which are arranged so that the frame can be placed with its outer edges projecting beyond the planes of the sides of the mould and so that the lower face of the frame is clear of and parallel to the flat bottom of the mould. A light weight concrete mix is then poured into the mould so that the mix fills the space between the bottom of the mould and the lower face of the frame and also fills at least part of the space bounded by the frame so that the steel members forming the frame are at least partly embedded in the mix. The mix is then allowed to set and the unit is removed from the mould. The mix is of such a constituency that, on setting, a smooth surface is formed in contact with the bottom of the mould. A unit is thus formed with the outer edges of the frame projecting beyond the concrete in-filling to facilitate the Welding together of adjacent units at right angles to each other, and with an inner face which is sufficiently smooth to serve as a ceiling or wall of a room without need of a further finish such as a plaster coating to be applied to the surface.

This invention relates to processes for making prefabricated units for use in erecting prefabricated buildings, and according to the invention, such a method comprises forming a structural steel frame, suspending the structural steel frame horizontally on the sides of a flat bottom open topped mould so that the outer edges of the frame project beyond the sides of the mould and so that the lower face of the frame is clear of and parallel to the fiat bottom, pouring into the mould a lightweight concrete mix so that the mix fills the space between the bottom of the mould and the lower face of the frame and also fills at least part of the space bounded by the frame so that the steel members forming the frame are at least partly embedded in the mix, the mix being of such a constituency that, on setting a smooth surface is formed in contact with the bottom of the mould, allowing the mix to set and removing the unit from the mould.

By suspending the structural steel frame in the mould with the outer edges of the frame projecting beyond the planes of the mould sides, a unit is formed with the outer edges of the frame projecting beyond the lightweight con crete in-filling. By arranging that the amount by which these outer edges project to be the same as the amount by which the smooth face of the in-filling projects beyond the face of the steel frame, when adjacent units are placed at right angles to each other, the outer edges of the steel frames will meet and the edges of the smooth faces of the concrete panels will also meet. This enables adjacent units to be connected by welding the touching parts of the steel frames without having to fill a gap between the concrete panels at the corners, the walls and ceiling of a room formed by such units being substantially continuous. The

3,611,533 Patented Oct. 12, 1971 ice structural steel frame may be suspended in the mould so that its lower face is between one half and one inch, preferably three quarters of an inch, from the bottom of the mould.

The structural steel frame is preferably formed by welding a number of similar tubular steel rectangular frame sections together to obtain the required sized frame. The tubular steel used may have a rectangular, square or circular cross-section. This steel frame, although supporting the lightweight concrete in-filling, actually acts as a reinforcement for the unit and takes all the stress and strain imposed on the unit.

The lightweight concrete mix preferably contains graded Leca aggregate and it is a further advantage of units in accordance wtih the invention that because of the smoothness and texture of the fiat surface of the unit, the units are suitable for use as inside walls and ceilings of a building without having to apply a plaster coating or other finish suitable for decoration. Leca is a trademark for a brand of lightweight sintered clay.

If the unit is intended to form a wall, the lightweight concrete mix is poured into the mould preferably at least until it fills substantially all of the space bounded by the frame, whereas if the unit is intended to form a ceiling, the mix is poured in until it fills about half the space bounded by the frame.

When the mix has set, the mould is preferably tilted until its bottom is vertical and the unit is then removed from the mould while in this position.

Wall units may be made containing doors and windows by fixing into the basic structural frame a door or window frame, which may be of wood or metal, and then casting the lightweight mix about the remainder of the structural frame. These wall units may also be formed with pipes and electrical junction boxes fitted in place.

Because of the simplicity of the method in accordance with the invention, the prefabricated units can be made quickly and cheaply, and furthermore, buildings constructed with these units can also be made quickly and cheaply.

In use, the units may be transported separately and erected on site or they may be assembled to form complete rooms before being transported to the site.

In the case of large sites, due to the simplicity of manufacture, a temporary factory, may be set upon site specifically for producing the units.

In assembly, four wall units are welded along their bottom edges to a floor frame which is constructed in the same way as the structural frames of the units. The floor is later completed by fixing boards across the top face of the frame. The wall units are welded together along their adjoining edges, and a ceiling unit is then welded to the top of the wall units.

When a house has been assembled from such prefabricated rooms or units, the outside walls may be bricked to give a more pleasing appearance to the house, and in such cases the wall units which form the outside walls may have the necessary wall ties for the bricking cast into the lightweight mix before it has set in the mould.

An example of a method of making a prefabricated building unit in accordance with the present invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic plan view of the structural support frame of-the unit positioned in the mould prior to the pouring of the lightweight concrete mix;

FIG. 2 is a section on the line 22 in 'FIG. 1 looking in the direction of the arrows, but after the lightweight concrete mix has been'poured; and,

FIG. 3 is a diagrammatic view showing how separate units are connected together to form a structure.

FIGS. 1 and 2 illustrate the formation of a 24 ft. x 8 ft. plane wall unit. Accordingly, a 24 ft. x 8 ft. structural tubular steel frame 1 is formed by welding six 4 ft. x 8- ft. rectangular tubular steel sections 2 together side by side. Each of these sections 2 is formed by welding together lengths of steel tubing 3, having a 2 inch square cross section, to form an 8 x 4 ft. rectangle, and is braced by 7 of an inch diameter steel reinforcing mesh 4 having 1 ft. square spacing, welded across the inside of the frame section 2.

The frame 1 is then laid horizontally in a rectangular mould 5 having a flat steel plate bottom 6, vertical sides and an open top.

The mould 5 comprises a fixed base 7 which supports a table 8 on which is mounted the flat steel plate 6 forming the bottom of mould 5. The table *8 is hinged along one edge 9 to the base 7 and can be raised to a vertical position by a hydraulic ram 10. Along the hinged edge 9 of the table 8 is a flange 11 which forms one of the sides of the mould 5. The other three sides of the mould 5 are formed by flanges 12, 13 and 14 on the fixed base 7.

Around the sides of the mould 5 is a groove 15, the lower face 16 of which is A of an inch above the bottom 6 of the mould 5. The parts on the flanges 12, 13 and 14 which form the upper face 17 of the groove are hinged, as at 18, so that the groove 15 can be opened.

With the groove 15 opened, the frame 1 is placed in the mould 5 with the edges of the frame 1 resting on the lower face 16 of the groove 15 and projecting about of an inch into the groove 15 all the way around. The groove 15 is then closed and the frame 1 is thus held firmly of an inch above the bottom 6 of the mould 5.

A lightweight concrete mix consisting of water, cement, fine Leca aggregate, and medium Leca aggregate in the volume ratios 3.6 to 1 to 3 to 5 respectively, is paddle mixed and then poured into the mould 5 to a depth of approximately 3 /2 inches, and thus completely envelopes the frame 1 in the mould 5. The mix 19 is allowed to set for about 12 hours. The groove 15 is then opened and the mould table 8 is raised by the hydraulic ram 10 until it is vertical, and the wall unit is lifted clear of the mould 5. The unit is left to stand in a vertical position for about a week before being ready for use. The face of the unit which was in contact with the bottom 6 of the mould 5 is smooth and flat, and serves as a finished surface for decoration.

Wall units having doors and/or windows in them can be made in the same way with the door and window frame being fitted into the structural frame 1 before the frame 1 is placed in the mould 5. The wall units can also be made incorporating utilities, such as water pipes, conduits for electric cables, electrical junction boxes, fixing brackets, and wall tiles etc., either by fixing the utility to the frame 1 or by placing it in position in the mould 5 before the frame 1 is placed in the mould 5.

In use, various units are connected together as shown in FIG. 3 to form a building. Firstly a floor unit 20 is laid, this unit comprising merely a frame structure which is similar to the frame 1 except that each section 2 is made from rectangular tubular steel with a cross section of 4 inches by 2 inches. Wall units 21 are then positioned around the edges of the floor unit 20, and the protecting lower edge of the frame of each unit 21 is welded to the adjacent edge of the frame of the floor unit 20, as at 22. The adjacent projecting frame edges of adjacent wall units 21 are also welded together. The projecting frame edges of a ceiling unit 23 are then welded to the upper frame edges of the wall units 21, as at 24. The ceiling unit 23 is formed by a floor unit which is the same as the unit 20 and which forms the floor for the above story, in which a Leca in-filling 25 has been set to a depth of 2 inches.

The flooring is completed by fixing floor boards 26 across the top of the floor units 20, 23.

Wall units 27 and a further ceiling unit 28 are then built on to the unit 23 in exactly the same Way. To give the exterior of the building a more pleasing appearance, a decorative wall 29 is built around the outside of the building, this wall 29 being tied to the outside wall units 21 and 27 by wall ties 30 which are cast into the units 21 and 27 during their manufacture.

I claim:

1. A process for making a prefabricated unit for use in erecting prefabricated buildings, comprising forming a structural steel frame having outer edge members and defining a pair of opposite faces, providing an open topped mould with sides and a smooth flat bottom, providing support means on said sides of said mould for supporting said outer edge members of said structural steel frame,.suspending said structural steel frame horizontally in said mould with said outer edge members of said structural steel frame supported on said support means so that said outer edge members project beyond the planes of said sides of said mould and with said pair of opposite faces of said structural steel frame disposed clear of said bottom of said mould and parallel to said bottom, forming a lightweight concrete mix, pouring said mix into said mould so that said mix fills the space between said bottom of said mould and the adjacent of said opposite faces of said structural steel frame and also fills at least part of the space bounded by said structural steel frame so that said frame is at least partly embedded in said mix, said mix being of such a constituency whereby, on setting, a smooth surface is formed in contact with said bottom of said mould, allowing said mix to set, and removing the unit from said mould.

2. A process as claimed in claim 1, wherein said support means defines a groove in said sides of said mould, said groove extending around said mould with the lower edge of said groove being at a constant height above said bottom of said mould, and wherein said structural frame is suspended in said mould with said outer edge members projecting into said groove.

3. A process as claimed in claim 1, wherein said structural steel frame is suspended in said mould with the lower of said pair of opposite faces disposed between a half and one inch from said bottom of said mould.

4. A process as claimed in claim 3, wherein said structural steel frame is suspended in said mould with the lower of said pair of opposite faces disposed three quarters of an inch from said bottom of said mould.

5. A process as claimed in claim 1, wherein said structural steel frame is formed by forming a plurality of similar tubular steel rectangular frame sections, placing said frame sections side by side to obtain the required size of frame, and welding said frame sections together.

6. A process as claimed in claim 5, wherein a steel reinforcing mesh is welded across the inside of each frame section to brace said section.

7. A process as claimed in claim 1, wherein said lightweight concrete mix is poured into said mould until it fills about half the space bounded by said structural steel frame.

8. A process as claimed in claim 1, wherein said light weight concrete mix is poured into said mould at least until it fills all of the space bounded by said structural steel frame.

9. A process as claimed in claim 1, wherein said lightweight concrete mix contains graded aggregate consisting of a lightweight sintered clay.

10. A process as claimed in claim 9, wherein said lightweight concrete mix comprises water, cement, fine aggregate consisting of a lightweight sintered clay, and medium aggregate consisting of a lightweight sintered clay in the volume ratio of 3.6 to 1 to 3 to 5, respectively.

11. A process as claimed in claim 1, wherein after said lightweight concrete mix has set, said mould is tilted until said bottom is vertical and said unit is then removed from said mould.

12. A process as claimed in claim 11, wherein after removal from said mould said unit is left to stand in a vertical position for about a week.

13. A process as claimed in claim 1, wherein said structural steel frame includes a door frame and said lightweight concrete mix is cast in the remainder of said structural frame.

14. A process as claimed in claim 1, wherein said steel frame includes a window frame and said lightweight concrete mix is cast in the remainder of said structural frame.

15. A process as claimed in claim 1, wherein any of the group of utilities comprising water pipes, conduits for electric cables, electrical junction boxes, and fixing brackets are arranged relatively to said structural steel frame whereby when said lightweight concrete mix is cast, said utilities are embedded in said concrete mix so that prefabricated units are formed incorporating said utilities.

16. A process as claimed in claim 1, wherein Wall ties are fixed to said structural steel frame whereby after said lightweight concrete mix has been cast, said wall ties project from the face of said unit furthest from said bottom of said mould.

References Cited UNITED STATES PATENTS Wertz 29l55 Sahlberg 29l55 Johnston 29l55 Mudd 29l55 Simmons 29l55 Melill 29l55 Kandra 29l55 Ellis 29-155 Edge 29l55 Richmond 29l55 Lowy 29l55 US. Cl. X.R. 

